Neat project! There are/were a lot of boards like this near the end of the era. I remember working on a system in the 80’s (cannot remember the make) that ran Turbo-DOS. I’m guessing it was an incantation of CP/M3 or MP/M. It was S-100 with a master Z80 CPU with 64K that controlled all the peripherals – floppy disk, hard disk, printers, etc., and it had a serial console. Then there was a slave Z80 card for each user with its own dedicated 64K RAM and serial I/O to user terminals. The master was the all-in-one card like you are describing. The machine was fully functional with just that card, an 8” floppy drive and a terminal. What you are describing sounds a lot like this brought up to modern standards, albeit with the same Z80.
I like the serial I/O concept, though ancient, can still be used with a lot of cheap, simple, terminal emulators. A while back (6 months?), I saw someone had built a terminal from a pair (I think it was a pair) of ATMega328’s. If I could re-discover that design, maybe it could be implemented on-board too. Then the PS/2 keyboard input makes sense.
I’ll also throw my suggestion in for more than 64K RAM so banked CP/M3 can be run. In nearly the same footprint (28 pin dip vs 32 pin dip), a 128 K or 512K RAM can be implemented. Then you’ll need a memory manager, but that can be done in 4 chips (my design, currently nearing completion), or maybe one chip if I can advance my design to a CPLD.
Finally, some kind of on-board disk would be absolutely marvelous. Maybe a Z80-bus-converted version of the IDE/CF board. And I might get shot down on this, but would it be all that difficult to also include a floppy interface? Perhaps others have a stash of floppies they might like to read? Or maybe they still have CP/M on floppy. Modern floppy interfaces, before they went down the obsolete road, were one ASIC.
My 3 cents.
Bob Bell
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of David Fry
Sent: Wednesday, September 09, 2015 4:11 PM
To: N8VEM-S100
Subject: [N8VEM-S100:7534] Re: A new Z80 based SBC to get beginners started on the S100 bus
the serial port console option also has its advantages in that the user could X-modem data from PC terminal across into the Z80 SBC memory space and do something usefull all from the one board..
David Fry
On Wednesday, September 9, 2015 at 8:34:51 PM UTC+1, monahanz wrote:
Guys, I thinking of trying to solve the chicken/egg problem by doing a single Z80 based S100 board that would contain 64K RAM, EEPROM, PS/2 keyboard input as well as a host of indicator LED's and jumpers to deactivate ROM/RAM keyboard etc. one at a time as other boards are added to get new people started on the S100 bus.
The only part I'm not sure of is what to do about console output/video. Was thinking of using the basic Propeller Console IO circuit
but this requires programming its two wire serial EEPROM with Parallaxes software and USB adaptor/software. Do you think that is outside the range capability of most
newcomers. Alternatively we could go with a straight serial output to some dumb terminal IBM PC terminal emulator. Open also to other suggestions.
John
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